纳米气泡电润湿形态变化

表面纳米气泡是现在的一个研究热点。本例发布纳米气泡的电润湿模拟。电润湿通过在近壁区施加一个力来等效电润湿。

该方法来自论文Atomistic simulations of electrowetting in carbon nanotubes，Nano Letters。可以看到当电润湿施加后纳米气泡的形态发生了很大的变化。

由于气体原子个数时固定的，当纳米气泡接触角减小的同时，气泡体积也大幅减小。这是符合拉普拉斯定律的。

通过这个设置可以研究电润湿对纳米气泡寿命的影响，以及纳米气泡内外扩散平衡的动力学过程。本例不需要data文件，建模在in文件中完成。

variable a loop 11

log log.$a

variable F index 0.00 0.05 0.10 0.15 0.20 0.25 0.30 0.35 0.40 0.45 0.50

dimension    3

boundary     p p p

units        real

atom_style   atomic

neighbor 2.0 bin

neigh_modify every 1 delay 0 check yes

pair_style   lj/cut 17

region box block 0 400 0 40 0 400 units box

create_box 3 box

lattice fcc  4.0

region solid block 0 400 0 40 0 20 units box

create_atoms 1 region solid

lattice fcc  6.5

region liquid block 0 400 0 40 23 300 units box

create_atoms 2 region liquid

group solid type 1

group liquid type 2

region del block 150 250 INF INF 20.1 60 units box

delete_atoms region del

lattice fcc  12

region gas block 100 300 INF INF 20.1 60 units box

create_atoms 3 region gas

group liquid type 2

group gas type 3

group fluid union liquid gas

mass 1 20.0

mass 2 20.0

mass 3 20.0

#in e_ss, e denotes epsilon; in s_ss, the first s denotes sigma, the second and third s denotes solid

#l denotes liquid; g denotes gas

variable e_ss equal 0.715077

variable e_ll equal 0.715077

variable e_gg equal 0.238359

variable s_ss equal 3.4

variable s_ll equal 3.4

variable s_gg equal 5.0

variable e_sl equal 0.1*${e_ll}

variable e_sg equal 0.476718

variable e_lg equal 0.25*${e_ll}

variable s_sl equal 0.5*(${s_ss}+${s_ll})

variable s_sg equal 0.5*(${s_ss}+${s_gg})

variable s_lg equal 1.62*${s_ll}

pair_coeff 1 1 ${e_ss} ${s_ss}

pair_coeff 1 2 ${e_sl} ${s_sl}  

pair_coeff 1 3 ${e_sg} ${s_sg}

pair_coeff 2 2 ${e_ll} ${s_ll}

pair_coeff 2 3 ${e_lg} ${s_lg}

pair_coeff 3 3 ${e_gg} ${s_gg}

fix 1 solid setforce 0 0 0 

minimize 0.0 1.0e-8 1000 100000

timestep 2.0

thermo 1000

compute myT fluid temp

thermo_style custom step temp

thermo_modify temp myT flush yes

velocity fluid create 300 5645354 temp myT loop local dist gaussian rot yes

dump mydump all atom 50000 atom_$F.lammpstrj

fix fxnvt fluid nvt temp 300.0 300.0 200.0

run 500000

region add block INF INF INF INF 20 23.5 units box

fix add liquid addforce 0.0 0.0 -$F region add

run 500000

reset_timestep 0

compute cc2 liquid chunk/atom bin/2d x 0.0 3.0 z 0.0 3.0

fix ave liquid ave/chunk 1 1000000 1000000 cc2 density/mass norm sample file rho_$F.profile

run 1000000

clear

next F

next a

jump system.in

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